The goal of the proposed trial is to test the impact of a novel practice-based intervention, including the use of personal digital assistant (PDA) based decision support, on adherence with a complex clinical practice guideline (CPG) in primary carepractices. We have chosen the Third Report of the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (ATP 111) guideline as it is complex, including screening criteria, risk stratification, and risk-group specific treatment recommendations. This randomized, controlled practice-based trial will test the primary hypothesis that intervention practices will have a net increase in the proportion of screened adults that is treated appropriately with lipid-lowering drug therapy. We will estimate the marginal cost effectiveness of the intervention for this primary endpoint. Other outcomes will include the proportions of patients that is appropriately 1) controlled to low density lipoprotein cholesterol goal, 2) screened, 3) risk-stratified, and 4) counseled regarding therapeutic lifestyle changes. We will explore the intervention effect on disparities in care observed at baseline. The intervention will be delivered at the level of randomization (the practice) and will include academic detailing and training on use of the PDA-based decision support tool. All practices (n=64) will receive usual care, consisting of guideline dissemination, baseline performance feedback, and continuing education. Outcomes will be assessed based on patient level data from baseline and follow-up chart reviews of adult patients (N-20,000) eligible for cholesterol measurement. Appropriate methods will be used to analyze these correlated data. Impact evaluation will be conducted via baseline and follow-up surveys of participating physicians and staff. Process evaluation will be conducted by tracking use of the PDA-based tool. We estimate as many as 48,000 major CHD events could be averted annually in the US with sufficiently improved adherence to ATPIII. If this intervention is successful, electronic decision support tools could be used to facilitate implementation of other complex CPGs. Hence, this innovative strategy holds great promise for making a substantial public health impact through the prevention of CVD and through subsequent translation to other important conditions.